1. Field of the Invention
The present invention relates to an exposed image input device, a printer apparatus and an image data input control program product and particularly to a technology of reading an image data saved in an image memory and inputting the read image data to an exposing device.
2. Description of the Related Art
Among electrophotographic printer apparatuses, there has been conventionally known the type in which an exposing device arranged to face a photoconductive drum includes a LED (light-emitting diode) array and the photoconductive drum is exposed with lines of light emitted from the LED array. Printer apparatuses of this type are called LED printers. The LED printer has a problem that lines of light emitted from the LED array, i.e. exposure lines are deviated from specified positions in some cases. The following three factors are known as causes of the deviated exposure lines.
The first factor is an angular error caused upon mounting the LED array on the printer apparatus. It is not easy to strictly conform a direction of a principal axis of the LED array to a main scanning direction and it is a usual practice to install the LED array in a transversely inclined state with respect to the main scanning direction.
The second factor is a deviation caused upon mounting LED chips forming the LED array on a substrate. It is ideal to linearly arrange the LED chips along the principal axis of the LED array. However, due to variations in a production process, there are cases where the LED chips are deviated from linearity to a certain degree.
The third factor is deviations of the respective LED chips from the main scanning direction caused by the distortion of the substrate, on which the LED chips forming the LED array are mounted, from linearity. It is not easy to ensure the strict linearity of the substrate while saving the production cost.
Conventional LED printers have ensured printing quality by compensating for mounting deviations by transferring image data to the LED array while displacing them in a sub-scanning direction according to the deviations of the respective LED chips. However, for duplex printing in the LED printer, it is necessary to temporarily save image data in the image memory alternately in forward order and reverse order page by page.
Japanese Unexamined Patent Publication No. 2004-82396 discloses an exposing device enabling duplex printing without alternately changing the order of transferring image data to an LED array in forward and reverse ones page by page. However, with a technology disclosed in this publication, it is not possible to realize duplex printing while correcting the deviations of LED chips.